Refractory container.



E. WBIINTRAUB. BEFRAGTOBY CONTAINER.

APrLIoATIoN FILED APB.. 11. 1912.

Patented lJune 3,1913.

Inventor:

l Izeczhiel Wemtraub,

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Application nled April 11, 19,152. Serial No. 696,112.

To all whom t may concern:

B ,e it known that I., Ezncnrnn WaINrReUB, f a cltrzen of the .United States, resdlng ati Lynn, county of Essex, State of Massachu- Sette, have invented certain new and usej ful Improvements 1n Refractory Containers, g

electric furnace.

of which the followingyis a specification.

The present inventmn relates to electricfurnaces and itS aim is to provide an envelop ,or container capable of withstanding highest temperatures' obtainable in ,the 'eleotrlc furnace' without fusing or giving Oif 5 1 .which I have `so Ifar been able to produce by chemically active vapors.

I have discovered that boron nitrid isf completely infusible at the highest heat ofi the electric arc, `and unites with this valu-, able property chemical -inertness and very;r high electrica resistance even at `the tem-` peratureof the carbon are. l have also discovered .that boron nitrid, especially when nly .divided has the propertyv of being selfthe punt. of this material maybe preserved whenana ln .containers of all kinds, such as tubes, crucibes, furnace lining and the like. In the accompanying drawing Figure 1 illustrates a resistance furnace and Fig. 2 an are furnace, each provided with boron nitrid linings atjthe zone of high temperature.

:One of the chief limitations to the more complete development of the broad field of.

chemical activity at very high temperatures which was opened up bytheA electric furnace has been the dittlculty of finding a material .for linings, crucibles and containers in general ,which could withstand very high temperature without fusing and without interacting with the Substance, Although ,many substances are described in the chemical literature as refractory or infusible, it is a matter of common knowledge that heretofore carbon has been the only material known to be actually `infusible in the in.;`

i tense heat of the electric arc.

7 The physical characteristics of boron "nitrid have not been investigated Carefully heretofore. The older chemists who have prepared the substance found that fit could not'bc melted in .an ordinary gas flame and called it nfueible in common with a large number 'nf other Substances. Modern retlle f' fplied no appreciable current uirements, among which prominently are te reqnlrernents of electric furnace'work, have set a new Standard So that at present the term infusible has received a .new meaning many substances formerly believed to Ibe :in-,lisible beiilig fused with ease in the oron nitrid, however, l have found stands in a class by itself,

l have found that, carbon excepted, boron jnitrd is the only substance which is actually infusble and a perently remains yundecomposed even at tlie highest .temperatures an arc. Unlikefcarbon, boron nitrid has no chemical aiiinity to most of the refractory materials which are liable to be used as a charge in such a furnace. I also vfound that the electrical insulating properties of boron nitrid at elevated temperatures are superior to those of any other known substance. To give an instance, some measurements made on a disk of boron nitrid about thickhave shown that at 1200o C. with 500 volts ap'- assed. For the sake of comparison it may e mentioned thaty a magnesium o Xid block of the same dimensions allows a considerable current to pass ,at'8000 C. with only 110 volts applied. No knowledge has existed of the electrical insulating value at high temperatures of 'boron nitrid. Other nitrids such as titanium nit-rid are conductors even at ordinary temperatures, and some nitrids such as silicon nitrid are easily decomposed by heat. Fig.

V"1 illustrates .how this combination of proporties of boron nitrid maybe utilized in a resistance furnace. The furnace here illus'- trated consists of a container l of iron, cop- Y per or other suitable metal in which' is a lining of boron nitrid 2 vhaving embeddedA v therein a lfairly stout wire 3 of tungsten or other refractory metal. One terminal 4 of this heater is attached to the metal frame lof the furnace and .the other terminal 5 1s insulated therefrom by an insulating -bushing ,as indicated. The cover 6 makes an air tight seal by the use of suitable gaskets 7.

The 'boron nitrid should heI heated in an linert environment such as 1n a neutral gas,

o r lin a vacuum. For this reason, the furnace is lprovided with pipes :Sand 9 which tivity of boron nitrid at high temperature enables the helix to -be operated at the highest temperatures obtainable with incandescent tungsten without appreciable leakage of current from turn to turn. Formerly, with the bestI refractory materials available,temperatures in excess of about magnesium,

17 00 C. could not\be attained in a resistance furnace. In a boron nitrid furnace, temperatures as high as the melting point of the most refractory heaters are obtainable.

Tungsten'melts at a temperature of aboutv 3200o C.

The arc furnace illustrated by Fig. 2 cons1sts of a metallic hood 11 standing upon a base plate 12, its end dipping into a bodyA of mercury contained in van annular trough 13. Situated within the hood and consti# ,tuting one` of the electrodes is av watercooled metallic cup 14 which is providedI with aterminal' 15 projecting through the.

base plate 12. Pipes 16 and 17 provide for: the ,introduction of a cooling fluid. Within th1s cup 1s a boron nitrid lining 18 in the center of which is supported a mass of maf;

evacuation, as above terial 19 which is to be melted and which? makes electrical contact with the inner wall of the rcup 14. Through 'the upper part ofthe .hood projects a water-cooled metallic electrode 20 which is insulated from the hood by any suitable means such as a rubber stopper-21 and silica tube 22. Attached to one end of the electrode 20 is a terminal 23 and to the opposite or arcing end is a cap 24 conslstlng of tungsten, graphite or other refractory material, the choice of materialv depending upon the purpose for which the furnace is to be used; Tubes 25 and 26 provide for the introduction of inert. gas or for indicated with respect to Fig. 1. In some cases it will be desirable to provide suitable cooling means for the outside vof the hood such asa Water jacket .or simply a blast of air' furnished by a fan. I nan arc, furnace as here illustrated it is possible to vmelt the most refractory metals such as tungsten, molybdenum, titanium and the like by means of an arc Without in -the vleast affecting the boron nitrid lining or urities into the tungsten. It is impossib e to accomplish this in a container consisting of any other known material. e.

Boron nitrid can be prepared by any one of the methods recommended in the literature, such as passing ammonia over boric introducing any im anhydrid mixed with calcium phosphate at a red heat or by passing ammonia over amorphous boron or by bringing together boron chlorid and ammonia and decomposing afterward the double compoundv formed. A way which I nd very convenient is to mix magnesium, nium chlorid in proportions of one part two parts boric anhydrid and three parts ammonium chlorid and heat this up to dull red and then wash the product. This method is described and claimed in a copending application, Serial No. 688,037 filed on April 2, 1912, by Richard Heyder. I ind, however, that no matter which one of these methods is used the productis not pure boron nitrid and this fact was more or less known to the chemists who prepared boron nitrid before. In methods starting with boric anhydrid, the only 'methods which are capable of giving large quantities of boron nitrid at a reasonable cost, the

boric yanhydrid and ammo-l boron nitrid produced contains oxygen;

probably the o'xy en is in form of boric anhydrid absorbed t(by boron nitrid or else in form of boron oxynitrid. It was found, however, that if this impure boron nitrid is heated up to a very high temperature, say betwen 1500 C. and 2500 C. the impurities, the chief of which vis boric anhydrid, volatilize out and an excellent-product is obtained which in many cases Where it is desired to reach very high temperatures is preferable to the impure boron nitrid. This method and product forms no part of my invention and is described and claimed in a co-pending Weintraub, 745,819.

February 3, 1913, Serial No.

application led by George by simply molding the boron nitrid in a suitable mold under a pressure of a few hu1 1.

dred pounds. TheL Yresulting article 1s strong, and can be easily handled.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. An envelop for a furnace operable at temperatures exceeding 17 00 C., consisting of a compressed mass of boron nitrid, which is chemically inert and infusible at the highest temperatures obtainable in Jsaid furnace.A

2. A molded envelop consisting of compressed self-bonded boron nitrid, which is inert, infusible and a substantial non-conductor of electricity at the highest obtainable temperatures.

3. The combination of an electrical workl ing conductor adapted to be raised to a high temperature, an insulating envelop thereforN consisting of compressed boron' nitrid and a metal casing surrounding and supporting said boron nitrid envelop.

4. In a furnace, a container consisting of boron nitrid, means for maintaining an intherefor, a metal casing therefor and means ert environment about said container and for introduclng an lnert gas lnto said caslng. 10

means for heating said container to tem- In Witness whereof, I have hereunto set peratures exceeding 17000 C. my hand this eighth day of April 1912.

5. In a heating device, the combination of EZECHIEL WEINTRAUB. an electrical Working conductor adapted to Witnesses: be raised to a high temperature, an insu- JOHN A. McMANUs, Jr.,

lating envelop of compressed boron nitrid FRANK G. HA'rrIE. 

